Impact stapling method

ABSTRACT

Method of impact stapling with an impact stapler having a staple with integral pointed target-penetration and securing forward section, rear hammer section, and medial compression shear section, the forward section having a threaded object-securing surface rearwardly of its pointed forward target-securing end. The staple is propelled into a target by a percussion-ignited propellant charge, and the forward section is secured by initial point penetration and subsequent compression shear of the medial shear section to enable the hammer section to impart a secondary securing impact to the forward section.

United States Patent 11 1 Monson Sept. 2, 1975 [54] IMPACT STAPLINGMETHOD 2,575,079 11/1951 Temple 85 28 3,377,903 4/1968 Korte 29/432 X[751 Invent $3 Mmmn, Glen 3,768,412 10/1973 Dardick 85/10 E x [73]Assignee: AAI Corporation, Cockeysville, Md. im y m C- Lanham AssistantExaminer -Victor A. DiPalma [22] Filed 1974 Attorney, Agent, orFirm-Reginald F. Pippin, Jr. [21] Appl. No.: 523,188

Related US. Application Data [57] ABSTRACT [62] Division of Ser 334 397Feb 21 973 Method of impact stapling with an impact staplerhavabandoned, which is a division of Ser. No. 180,333, ing a Staple Wiihintegral Pointed iargei-penetraiiw Sept. 14, 1971, abandoned, andsecuring forward section, rear hammer section, and medial compressionshear section, the forward 52 us. 01 29/432; 29/526; 85/10 E; Sectionhaving a threaded Object-Securing surface 5 49; 227 9; 227 10 rearwardlyof its pointed forward target-securing end. 51 Int. Cl. 323p 11/00 'I11estaple is propelled into a target y a Percussion- [58] Field Of Search29/4321, 432, 432.2, 526; ignited propellant charge, and the forwardsection is 85/10 E 10 R 49 28 61; 227/8 9 1O, 11 secured by initialpoint penetration and subsequent compression shear of the medial shearsection to en- [56] Referen Ci d able the hammer section to impart asecondary securimpact to the forward section.

2,166,041 7/1939 Cox 227/9 2 Claims, 8 Drawing Figures PATENTED SEP 2 75SHEET 2 OF 2 Au'lllll FIG. 6

IMPACT STAPLING METHOD This is a division of application Ser. No.334,397 filed Feb. 21, 1973 now abandoned, which in turn is a divisionof application Ser. No. 180,333 filed Sept. 14, 1971, now abandoned.

This invention relates to a method of stapling with impact staplingarrangements which may be utilized to effect securing of an object to atarget piece which may be formed of high-strength relativelylow-elasticity steel or the like.

Handheld staplers have heretofore been made for attaching a metal sheetor other object, such as a bracket, to a target in the form of a steelplate, such conventionally incorporating a high-strength steel studstapled to the target and utilized as a bolt or tension member to fastenmetal sheets, brackets, or other items to the target. A primary problemassociated with this type of connection is the fastening or retention ofthe stud to the target. This has been accomplished by the partialpenetration and embedment of a knurled tapered point end on the studstaple into the target material, utilizing a hand-held holder andpropellant powder for imparting stud penetration. Typical stud firingvelocities of 750 to 800 feet per second have been utilized withhand-held stapling arrangements. At this velocity, the stud staple maypenetrate the target sheet to a depth of 0.4 inches, which is asufficient depth to imbed the point and knurled surface thereon into atarget sheet of relatively low-strength, high elasticity steel, andthereby achieve a nominally satisfactory structural joint between thestud staple and the target sheet. In this respect, the stud is retainedin the target material of this type due to the ability of the elastictarget material to deflect in a radial direction during stud penetrationand then to elastically flow back over the stud knurl, therebyentrapping the stud in the target sheet. The target material entrappingthe knurled point stud staple with the target provides a stud retentionwhich will resist tension pull-out loads ofa sometimes accept able orderof magnitude, as for instance up to 2200 pounds. However, with the priorart methods and arrangements of this type, such have been found to beuseful only in low-strength steel target plates of up to 1 inchthickness, as above this thickness the rebound energy of the stud is ofsuch a magnitude that it exceeds the transient gripping forces duringpenetration and rebound, and results in the stud bouncing out of thehole or its being loose in the target'material, with relatively low andineffective joint strength.

This prior art stapling arrangement and method depends on the elasticityof the steel target material in order to achieve intimate materialcontact between the knurls of the staple and the hole surface of thetarget material. It is also dependent on the area of this contact inorder to provide a joint of effective structural quality. Among thedisadvantages inherent in this prior art method of stapling, in additionto those noted above, are that the knurled stud point used forjointconnection is inherently an inefficient penetrator which must be ofsufficient size and driven to a sufficient depth in the steel target soas to insure that the knurls of the stud .are effectively engaged by thetarget material.

To attempt to drive this inefficient configuration into a steel targetrequires a high level of energy to achieve ing power with a given targetmaterial, or with respect to its use against targets of thicker steelsand/0r higher strength steels, would require even higher levels ofenergy, which levels of energy would produce excessive recoil loads forhand-held operation, which is a particularly desirable form of operationin some instances such as in underwater use. In addition, such higherlevels of energy being imparted to the stud staple impose stringentdesign criteria on the stud staple firing device and produce highstructural loads on the stud staple during penetration, which highstructural loads may cause unpredictable degradation of the stud staple.In addition, in utilizing this prior art arrangement the steel targetmaterial must be sufficiently elastic to properly engage the knurls ofthe stud penetrating section, and this condition precludes its use forstapling to higher strength but less elastic steels, as the strength ofthe joint is relatively low in such instances, if the joint is effectiveat all, as the joint strength is basically determined by the smallamount of target material which entraps the stud knurl. Further, thisprior art arrangement provides essentially little or no capability forfastening to steel target plates of 1 inch or thicker, even withrelatively lowstrength more elastic steels.

It is an object and feature of this invention to effect a substantialimprovement in the stapling methods, and particularly to provide amethod utilizing arrangements which may be hand-held in order to achievehigher strength joints in relatively high-strength steels, independentof thickness, with energy requirements compatible with hand-heldoperation.

It is a further feature to provide an improved staple method whichenables the utilization of a smooth pointed penetrator as the jointconnection, without the requirement for knurls or the like at the zoneof joint connection between the target and the stud staple, and in whichthe stud staple may be effectively secured to target materials ofhigh-strength low-elasticity steels and/or steels of infinite thickness.

Still a further feature is the provision of a stapling method which isemployed in conjunction with a staple .so as to cause the staple toimpart a self-operated sec ondary impact for improved fastening to atarget.

A further object and feature is the provision of an improved impactstapling or nailing method employing secondary self-impacting of apenetrator section of a staple or nail after and as a function ofexternal driveimpacting of the staple or nail.

Still other objects, features and attendant advantages will becomeapparent to one skilled in the art from a reading of the followingdetailed description of a preferred mode of practice in accordance withthe invention, taken in conjunction with the following drawings wherein:

FIG. 1 is a longitudinal section view of a stapling or nailingarrangement employed according to the invention.

FIG. 2 is a fragmentary side view of the upper section of thearrangement of FIG. 1, taken as viewed from the righthand side of FIG.1.

FIG. 3 is an enlarged view in perspective of the firing pin in thearrangement of FIG. 1.

FIGS. 4, 5 and 6 are schematic section views illustrating sequentialsteps in the method according to the invention, utilizing thearrangement of FIG. 1 in securing the stud staple to a target plate.

FIGS. 5a and 6a are enlarged views in partial section of the medialshear section of the staple or nail during carrying out of the methodaccording to the invention, and corresponding to the shear rupture andsecondary self-impacting conditions illustrated respectively in FIGS. 5and 6.

Referring now in detail to the Figures in the drawings, a staplecartridge arrangement for utilization according to the method inventionis generally indicated by the reference numeral 11, and includes acartridge barrel 13 having a frangible seal 15, and within the bore 13aof which is disposed a staple or nail generally indicated at 31, whichin turn is secured as by a retaining pin 39 to a pusher generallyindicated at 41. Pusher 41 is in turn connected through a shear pin 49to a propellant cup base 51 which is threadedly secured in the rear endof barrel 13, and which houses a percussion primer 53 and charge ofignitable propellant mix 55.

The cartridge 11 is removably secured within the bore 91a of a hand-heldholder 81 which is closed at the closure 85 has a central recess 85b onits interior face, which recess is preferably of sufficient crosssection to accommodate passage of the smooth pointed penetrator section31a of the staple 31 and of less diameter than the outer thread diameterof a threaded securing section 31b rearward of the tapered point 31a. Apuncturable closure membrane 85a is formed across the bottom of therecess 85b, and is punctured by the staple 31 in the course of firingthe cartridge 11, the walls of recess 85a then engaging with threadedsecuring section 311).

Securing of the cartridge 11 within the holder 81 is suitably effectedby set screws 91 which engage with the exterior of the cartridge 11rearwardly of a damping and center ring 16. A guard 87, with O-ringseals 89, may be secured over the area of set screws 91, through themedium of a set screw 93, thereby affording a substantially water-tightseal at this point between the bore 81a of the holder 81 and theexterior of the holder, and enabling the device to be moreadvantageously used underwater if so desired. 7

Disposed rearwardly of the cartridge 11 in the bore 810 is a firing pinwhich is held in the cocked position as shown in FIG. 1, against theaction of compression spring 65, through the medium of aretention/release pin 71. The retention/release pin 71 is held in theretention position by a safety handle 101 which longitudinally slidablyengages therewith from the lower side, the safety handle 101 having abifurcated end which extends between the enlarged head of the pin 71 andthe exterior body of handle 81 to prevent movement of the pin toward thehandle 81 until removal of the handle is effected preparatory to firing.A safetypin 103 extends through lateral holes in pin 71 and handle 81,and I may be selectively removed by exerting a pulling force thereonwith a pull ring 105, after which the safety handle may be sliddownwardly along the holder 81 for removal. In the normal safetyposition, the safety'handle is prevented from being angularly movedabout the axis of pin 71, through engagement of a pin 101a on the safetyhandle with a guide slot 81b on the outer surface of the handle 81.

The actuator retention/release pin 71 retains the firing pin 61 in thecocked position by engagement of retention sections 73 thereof withenlarged release holes 61r, 61R formed in the opposite walls ofcup-shaped firing pin 61, these retention holes being best seen in FIG.3, and the retaining relationship being illustrated in FIG. 1.Immediately adjacent the retention sections 73 of pin 71 are reducedneck release sections 75, which are of sufficiently small diameter topass freely through release slot sections 61b, 61b formed in the upperend of the cup-shaped firing pin 61, to thereby enable the firing pin tomove downwardly upon the movement of the release pin 71 to the left by asmall incremental extent after removal of the safety handle 101. Thereduced neck release sections 75 are caused to be in registry with therelease slots 61b, 61b by engagement of a shoulder stop 72 on therelease pin 71 with the exterior surface of handle 81 when the pin 71 ismoved to the left, as viewed in FIG. 1. O-ring seals 77 may be employedadjacent the internally opposite ends of pin 71 to afford water-tightsealing of the interior bore 81a of handle 81.

Upon registry of the reduced neck release sections 75 of pin 71 with theenlarged retention holes 61r, 6lr, the firing pin will move forwardunder the influence of the compression spring 65, being guided in thisrespect by a set screw guide pin 94 which slidably engages with guideslot 61a formed as a lower extension of release slot 61b and enlargedretention hole 61 in the firing pin 61. The firing pin 61 may have oneor more fluid bypass orifices 63 formed in its forward end to enablefluid pressure equalization, and thereby enable fullutilization of thefiring pin force exerted by compression spring 65.

Upon impacting of the firing pin 61 with the primer 53 the propellantmix 55 will be ignited to effect shearing of the shear pin 49 andmovement of the pusher 41 and staple 31 downward as viewed in FIG. "1,it being arated by annular grooves 410, these rings and grooves servingthe dual purpose of aiding in sealing the propellant gases and alsoenabling final energy absorbing stopping and retention of the pusher 41within the forward end of cartridge 11. To this end, there is formed atthe forward end of bore 13a in cartridge barrel 13 a shoulder stop 11awhich enables the free passage therepast of the staple 31, whileengaging the shear stop rings 41b, thereby causing the rings 41b to besheared as the pusher 41 attempts to move therepast, the number of ringsbeing sufficient to absorb the remaining en ergy in the pusher 41 afterstaple 31is secured to the target, and to retain the pusher within thecartridge barrel 13 at the end of the firing sequence.

As noted heretofore, the staple or nail 31 is formed with a penetratorsection 31a which takes the preferred form of a smooth tapered securingpoint 31a, rearwardly of which is a threaded securing section 31b whichis of substantially constant thread diameter along its length, tothereby simulate a threaded stud end when the staple 31 is embedded in atarget sheet, with the threaded securing section 31b protruding on theexterior of the target. The staple 31 is formed as an integral unit witha rear hammer section 31d connecting with the forward penetrator section31a and threaded securing section 31b through a reduced diameter shearsection 310. A plug 42 may be employed, if desired, rearwardly of hammersection 3111 to absorb shock and forward motion force between the hammersection 31a and pusher 41.

The reduced diameter shear section 310 is formed with a sufficientdiameter to provide the necessary column strength between the penetratorand threaded nut or washer-securing sections 31a, 31b on the one handand the hammer section 31d on the other hand, to insure that thenecessary precise force is imparted from the pusher 41 to the penetratorsection 41a to afford desired penetration of the point 31a into a targetsheet. With a high tensile steel target (eg 100,000 psi ultimate tensilestrength), a desired and proper extent of penetration by a point havinga length of 0.45 inch and a rear diameter of 0.230 inch, has been foundto be approximately O.35 inch. To effect this extent of penetration,using a one-piece high-strength steel (eg, maraging steel 300) staple31, a diameter of approximately 0.150 inch for the frangible section hasbeen found satisfactory, with a 0.280-inch diameter hammer section 31dand threaded securing section 31b thereadjacent. After'the proper depthof penetration of point 31a has been effected during initial impact,increased resistance by the target to further point penetration causesthe frangible reduced diameter shear section 31c to fail in compressionshear, and the hammer section 31d will continue forward to impart afurther secondary impact to the rear of the integral point and threadedsecuring sections 31a, 3ld, as illustrated in FIGS. 5 and 6respectively, as well as enlarged FIGS. 5a and 6a, the

j metal object sheet 121 and thexmetal target plate 131,

an effective degree of penetration being illustrated in target plate131. At this position, the resistive forces of the target plate 131 aresufficient to overcome the column strength of the shear section 31,thereby effecting the shear rupture as indicated at 3lcs. The remaining.kinetic energy of the pusher 41 and hammer section 1 31d will thereuponcause the hammer 31d to effect a secondaryimpacton the rear end of thepenetrator and threaded securing sections 31a, 3 l b, to therebyprev'ent- I the pe netrator point section 31a from bouncing out of itspenetration contact with the target 131, and also afvfords a furthersecuring action at the point of contact with the point section 310 andthe target 131. The thus embedded point is effectively secured with thetarget plate, being frictionally secured and apparently to some extentwelded to the target material. It has been found that with anarrangement of this nature the staple may be effectively secured towithstand an axial pull of approximately 6,000 pounds, and such has beensuccessfully used as a fastener to mild steel, 4130 steel, HY steel, andHY steel, in thicknesses ranging from inch to effectively infinitethickness.

While the invention has been described with respect to its practice witha single preferred embodiment, it will be apparent that variousmodifications and improvements will be made without department from thescope and spirit of the invention. For instance, while the method isdescribed and illustrated as applied with an illustrative apparatus inwhich there is disclosed a particular means for actuating the latentenergy means, it isnot necessary that such be a part of the manufacturedapparatus, nor that such be sold or furnished to a user with such anactuating means. The actuating means could be added or supplied later attime of use, or actuation could be accomplished manually as with amanually wielded hammer or other impact, electrical, chemical reaction,or other desired type of device, which might suitably fire or otherwiseactuate a primer. propellant charge, spring, or other latent energymeans. Various separate auxiliary apparatus, both mechanical andelectrical, for firing or otherwise actuating primers,

propellant charges, etc., or other latent energy means, are well known,as in the ordnance art, and are not necessary to be described for anunderstanding of this invention as to scope or manner of alternativepractice thereof by one skilled in the art. Additionally, while theillustrative apparatus utilized in carrying out the method employslatent energy means in the form of ignitable propellant, it will beappreciated that other latent energy means might suitably be employed,such as a spring, a selectively releasable suspended weight movableunder force of gravity, a chemical composition or compositions whichgenerate useful energy such as gases and/or heat upon selective chemicalreaction, etc. Further, while practice of the method with the specificillustrative apparatus has been illustrated and described, and has beenfound to be a desirable mode of practice, and while various detailedfeatures of such apparatus may themselves be additionally novel andinobvious, the broad invention of my double impact nailing method withan impact-compression-shearable double impact nail unit clearly does notrequire the particular structural arrangement of the illustrativeapparatus,

such as the sealed barrel 13, hand-held holder 81, car

tridge 11, pusher 41, primer-ignited propellant powder latent energymeans 55, safety firing pin arrangement -63, 73, 75, 101., 105, orenergy-absorbingshear ring arrangement 41b, 1 la. For example, fornormal use outside of underwater use, a sealed barrel is not necessary,and the initial external drive force for imparting initial penetratingvelocity to the staple or nail unit 'may be imparted directly to thenail unit without use of a pusher 41, as by a spring, a weight impartedthereagainst, or a chemical or electrical energy-generating andforce-transmitting reaction. Accordingly, the in-' vention is not to belimited by the illustrative embodiment, but only by the scope of theappended claims.

I claim: 1. The method of attaching a staple unit to a target,comprising imparting a forward velocity to an impact staple having aforward point section, a hammer section and a medial compression shearsection between said point section and said hammer section, said forwardvelocity being in the direction of a target mass,

impacting said staple unit at its forward point section with said targetmass,

compression shearing said medial compression shear section by inertialmass kinetic energy action of said hammer section on the rear of saidshear section upon impact of said forward point section with said targetmass,

and forwardly impacting said forward point section by the continuedforward inertial mass kinetic energy movement of the resultantcompression-shearseparated rear hammer section of said staple.

2. The method of attaching a staple or nail unit to a target, comprisingimparting a forward velocity to an impact staple or nail having aforward point section and a rear inertial masshammer section, saidforward velocity being in the direction of a target mass,

impacting said staple or nail unit at its forward point section withsaid target mass,

compression shearing said staple unit intermediate said forward pointsection and said rear inertial mass hammer section by inertial masskinetic energy action of said hammer section upon impact of said forwardpoint section with said target mass,

and forwardly impacting said forward point section by the continuedforward inertial mass kinetic energy movement of the resultantcompression-shearseparated rear hammer section of said staple or nail.

1. The method of attaching a staple unit to a target, comprisingimparting a forward velocity to an impact staple having a forward pointsection, a hammer section and a medial compression shear section betweensaid point section and said hammer section, said forward velocity beingin the direction of a target mass, impacting said staple unit at itsforward point section with said target mass, compression shearing saidmedial compression shear section by inertial mass kinetic energy actionof said hammer section on the rear of said shear section upon impact ofsaid forward point section with said target mass, and forwardlyimpacting said forward point section by the continued forward inertialmass kinetic energy movement of the resultantcompression-shear-separated rear hammer section of said staple.
 2. Themethod of attaching a staple or nail unit to a target, comprisingimparting a forward velocity to an impact staple or nail having aforward point section and a rear inertial mass hammer section, saidforward velocity being in the direction of a target mass, impacting saidstaple or nail unit at its forward point section with said target mass,compression shearing said staple Unit intermediate said forward pointsection and said rear inertial mass hammer section by inertial masskinetic energy action of said hammer section upon impact of said forwardpoint section with said target mass, and forwardly impacting saidforward point section by the continued forward inertial mass kineticenergy movement of the resultant compression-shear-separated rear hammersection of said staple or nail.